A new study has found that Vitamin E supplements may cause thinning of the bones.
From studies in laboratory animals it was found that the most common form of vitamin E stimulates the generation of bone-degrading cells. Scientists who carried out the research in Japan are now calling for their results to be followed up in humans.
Thousands, possibly millions, of people in the UK take supplements of vitamin E, a powerful antioxidant. In the US, more than 10% of adults take the vitamin every day. The most common form of the vitamin, both in supplements and natural sources such as olive and sunflower oil, is alpha-tocopherol. Its health benefits are said to include reducing the risk of heart disease, cancers, cataracts and age-related mental decline, but the evidence for such claims is not well outlined even in large studies and controversies exist.
Bone is constantly changing, with old bone broken down and new bone being built. Osteoporosis occurs when old bone is broken down by the body far more quickly than it is replaced. This new study found that bone “remodelling” - the maintenance of bone by balancing its formation and breakdown could be affected by vitamin E. When bone is broken down, specialist osteoclast cells cause its minerals to be released and recycled into the body in a process called “resorption”. The study suggests that while vitamin D promotes bone generation, alpha-tocopherol vitamin E performs the opposite role.
Researchers led by Dr Shu Takeda, from Keio University in Tokyo, found that genetically modified mice with low blood levels of the vitamin developed excessively high bone mass. This was found to be due to lower levels of bone resorption, rather than greater bone formation. When vitamin E was added to the animals' diet, their bone density returned to normal. Normal mice given alpha-tocopherol vitamin E supplements at doses equivalent to those taken by humans showed a 20% reduction in bone mass after eight weeks.
“Bone health is a dynamic tissue and issue,” said Dr. Robert Graham, an internist at Lenox Hill Hospital in New York City. “It is in a constant struggle between osteoblasts ... and osteoclasts.” Understanding this cellular battle “is crucial in understanding how vitamin E may affect our bone health,” Graham said.
The findings are published in the latest online edition of the journal Nature Medicine. Dr Takeda's team found that alpha-tocopherol stimulated the fusion of osteoclast precursor cells - the first step in osteoclast formation.
The researchers wrote, “In summary, we show that vitamin E stimulates bone resorption and decreases bone mass by inducing osteoclast fusion. Moreover, we provide evidence that serum vitamin E is a determinant of bone mass. Given the widespread use of vitamin E, and especially alpha-tocopherol, as a supplement in humans, a larger, controlled study that addresses its effects on human bone is warranted.”
The study has revealed “the opposite of what was traditionally believed,” Graham said. “This is intriguing, because previous in vitro [laboratory] studies and mice studies have yielded contradictory results.” Still, much more research is needed to better understand how vitamin E works in the skeletons of humans, Graham added. “Before we start telling people to throw away their vitamin E, let me state that these results are in mice and more studies are needed to see the risks and benefits in humans,” he said.
One of the world's most popular supplements, it is taken daily by hundreds of thousands, if not millions, of Britons. In the US, more than one in ten adults take vitamin E tablets. An estimated three million Britons have osteoporosis, with 230,000 breaking weakened bones each year and 1,150 dying each month after fractured a hip.
Professor Helen MacDonald, an advisor to the National Osteoporosis Society, said, “There is nothing to worry about if you are getting plenty of vitamin E from your diet but those taking high doses of the nutrient in supplements need to be wary. You have to remember this research was carried out on animals and findings in humans can be very different. But more research is needed.”